Field of the Invention
The invention relates to a Schottky diode assembly including a Schottky contact formed on a semiconductor substrate and having a semiconductor region of a first conductivity type, a metal layer disposed adjacently on the semiconductor region, a protective structure constructed on a peripheral region of the Schottky contact, and a doped region constructed in the semiconductor substrate and having a second conductivity type of opposite polarity from the first conductivity type, the doped region extending from a main surface of the semiconductor substrate to a predetermined depth into the semiconductor substrate. The invention also relates to a method for producing such a Schottky diode assembly.
In order to improve the depletion properties of a Schottky diode, it is known to diffuse a guard ring, of opposite conductivity to the semiconductor region of the diode, at the peripheral region of the metal-to-substrate junction. That produces a graduated p-n junction at the diode edge, so that leakage currents can be reduced. In the case of an n-doped silicon epitaxial layer for the diode semiconductor region, the guard ring is p-type conductivity. As a result of that provision it is possible to successfully adjust the depletion currents of a Schottky diode uniformly over the production of the diode and at the lowest level for a particular diode type. In order to optimize the breakdown voltage for a predetermined diode type, the doping of the guard ring should be as low as possible and diffused as deeply as possible, yet should be located above the level of the epitaxial doping so that the p-n junction is effective. However, low doping of the guard ring at the boundary surface with the dielectric disposed adjacent the metal-to-substrate contact increases the danger of channeling at that boundary surface, which results in an increase in the depletion current of the diode and the capacitance.